1. Field of the Invention
The invention relates to optical inspection, in particular, to an optical coherence tomography (OCT) apparatus and an OCT apparatus operating method capable of providing an optical path difference and a light frequency changing effect.
2. Description of the Prior Art
In recent years, with the development of the optical inspection technology, an optical image scanning technology provides a non-invasion way to know the structure and composition of the item to be inspected, and it is widely used in medical diagnosis due to its features of rapidity and non-invasion. When a light is emitted into the structure of the item, the absorption characteristic and scattering characteristic of the light will be changed in the medium with different depths. The optical image scanning technology is to use different optical methods to obtain the information carried by the scattered photon in the structure of the item to obtain a high-resolution image.
In general, a medical imaging technology is to measure the physical characteristic changes generated after a physical field source is provided to a biological tissue, and convert them into visual images to help the doctor to judge whether the structure of the biological tissue is formal and dynamically make a functional evaluation, so that the rapid and correct diagnosis and treatment can be provided to enhance medical quality. And, the medical imaging technology is currently developed toward the directions of using non-ionizing energy field source, measuring the image in the non-invasion way, having high space resolution and high contrast resolution, and real-time imaging capability.
Among the known medical imaging technologies, a medical imaging technology called “optical coherence tomography” (OCT) is developed rapidly and used in many application regions. The OCT technology is also called “optical biopsy” and uses a low coherence light source and a measurement structure of changing optical path difference interferometer to measure the coherence characteristic of the back-scattering light field strength of the biological tissue, and further to form a 2-D image or 3-D image. Therefore, the OCT technology can meet the development directions of the medical imaging technology, and many research groups pay attentions to it, so that the OCT technology is developed rapidly and used in many application regions.
In practical applications, since the OCT technology has the advantages of high resolution, high sensitivity, non-ionizing energy field source, and low cost, and the OCT technology can measure the cross-sectional structure of the tissue in the item and flowing velocity distribution diagram to provide the micro-meter level high resolution image. Therefore, the OCT technology has great help to diagnose the disease of the tissue and position the structure of the cell, for example, the retina of the eyeball.
Please refer to FIG. 1. FIG. 1 illustrates a schematic diagram of a conventional OCT apparatus. As shown in FIG. 1, the OCT apparatus uses the Michelson interferometer to divide the coherent light emitted from the coherent light source 10 into two light beams via the light splitter 12: one light is emitted to the reference end 16c and reflected by the reference end 16c; the other light is emitted to the item to be inspected T and reflected by the item to be inspected T. These two reflected lights will be passed through the light splitter 12 and transmitted to the light sensor 17, and the computer 18 will calculate the optical path difference between these two reflected lights and obtain a vertical cross-sectional optical data related to the item to be inspected T according to the optical path difference. In fact, the light sensor 17 can be a spectrometer, optical lens set, or any other devices having the light sensing function.
In addition, please refer to FIG. 2. FIG. 2 illustrates a schematic diagram of the basic structure of the OCT apparatus of FIG. 1. In order to generate the optical path difference between the reference end 14 and the item to be inspected 16, the OCT apparatus 1 needs some complicated optical devices, for example, an optical grating system, a rotation mechanism, and a light source 10 having changeable frequency, and also needs a shifting or rotating mechanical structure to generate the optical path difference. FIG. 2 also shows that the conventional OCT apparatus 1 changes the position of the reflection mirror 14 (moving parallel to the z-direction of FIG. 2 or rotating) to obtain different optical path differences, and obtain the sensing result of the item to be inspected 16 in the direction of depth (the z-direction of FIG. 2) through the Michelson interference effect.
No matter the OCT apparatus in FIG. 1 or the OCT apparatus in FIG. 2, a shifting or rotating mechanical structure will be necessary to generate the optical path difference, not only the cost of the OCT apparatus will be increased, but also the structure of the OCT apparatus will become complicated, and its volume will also become huger. Therefore, the invention provides an OCT apparatus and an operating method thereof to solve the above-mentioned problems.